Railway signaling system



June 9, 1942. F. H. NICHOLSON 2 286,002

RAILWAY S IGNALING SYSTEM INVENTOR' Fra'nkllzl" U012.

HIS ATTORNEY Patented June 9, 1942 RAILWAY SIGNALING SYSTEM Frank H.Nicholson, PennTownship, Allegheny County, Pa., assignor to The UnionSwitch & Signal Company, Swissvale, Pa., a corporation of PennsylvaniaApplication March 2'7, 1941, Serial No. 385,400

15 Claims.

My invention relates to approach control apparatus for use in railwaysignaling systems of the coded track circuit class, and it has specialreference to the provision of improved apparatus for approachcontrolling various signaling functions without the use of line wires.

It is an object of my invention to provide an improved system of thetype described which is arranged so that energy stored in the trackcircuit cannot produce improper operation of the relays employed in thesystem.

A further object of the invention is to provide an improved system ofthe type described which is arranged in such manner that the detectorrelay employed therein cannot be improperly energized from the trackbattery in the event the coding device contacts which control thecircuits of the detector relay Winding and of the track battery fail tointerrupt one of these circuits before establishing the circuit of theother.

Another object of the invention is to provide an improved system of thetype described which is arranged in such manner that the track relayemployed therein cannot be improperly energized from the impulse orfeed-back battery in the event the impulse relay contacts which controlthe circuits of the track relay and of the battery fail to interrupt oneof these circuits before establishing the other.

Other objects of my invention and features of novelty will be apparentfrom the following description taken in connection with the accompanyingdrawings.

I shall describe one embodiment of my invention together with severalmodifications thereof which I may employ and shall then point out thenovel features thereof in claims.

In the drawings,

Fig. 1 is a diagram of a section of railway track equipped withapparatus embodying my invention,

Fig. 2 is a diagram of a modified form of apparatus which may beemployed at the entrance end of the track section,

Figs. 3, 4, 5 and 6 are diagrams showing modified forms of apparatuswhich may be employed at the exit end of the track section,

In the drawingssimilar reference characters refer to similar parts ineach of the several views.

Referring to the drawings, there is shown therein a section of railwaytrack having track rails l and 2 over which traflic normally moves inthe direction indicated by the arrow, that is from left to right. Thetrack rails of each section are separated from the rails of theadjoining sections by insulated joints 3 in the usual manner.

The track section has at the entrance end thereof a track relay TRhaving a winding receiving energy over the section rails. This relay isof a type the contacts of which become picked up on the supply of energyof one polarity only to the relay Winding. The track relay TR hasassociated therewith a decoding transformer DT, an impulse relay IR, abattery IB from which impulses of feed-back energy are supplied to therails of the track section, and an auxiliary relay H. The relay H may beemployed in the manner well known in the art to control the supply ofenergy to the adjacent section in the rear and to control the signal,not shown, at the entrance end of the section.

The equipment at the exit end of the section includes a detector relayKR, a track battery TB, a coding device CR, an approach relay AR, and atransformer KT.

The detector relay KR is of the polarized type and has movable contactswhich are shifted to their left-hand or normal position when the relayWinding is supplied with energy of the polarity of the impulses ofmaster code, while these contacts are shifted to their reverse orright-hand position when the relay winding is supplied with energy ofthe other polarity, that is energy of the polarity of the impulses offeed-back energy. In addition, the relay KR if of a type the contacts ofwhich when moved to either position will remain in that position untilthe relay winding is energized with current of the polarity effective tomove the relay contacts to their other position.

The relay CR is provided with contacts which are continuously picked upand released at one or another of a plurality of different ratesdepending upon traffic conditions in advance. One means for controllingthe relay OR is shown in Fig 5 of United States Patent No. 2,174,255 toHerman G. Blosser.

The approach relay AR may be employed to control circuits for energizingthe lamps of the signal, not shown, for the adjacent section in advance,or to control circuits for any other appropriate purpose.

The equipment is shown in the condition which it assumes when the tracksection is vacant. At this time the contact ID of the coding relay. CRis continuously moved between its picked-up and its released positions.When this contact is in its picked-upposition, the track battery TB isconnected across the rails l and 2 by a circuit which includes in seriestherewith the relay KR.

The contacts of the impulse relay IR are released at this time so thatcontact 52 connects the track relay TR across the rails l and 2.Accordingly, energy from the track battery TB flows through a circuitwhich is traced from the positive terminal of the battery through frontcontact ill of coding relay CR, winding of detector relay KR, track raill, winding of track relay TR, back contact E2 of impulse relay IR, trackrail 2, and resistance M to the negative terminal of the track battery.As a result of this fiow of energy, the relays KR and TR are energizedin series. The polarity of this energy is such that it is effective topick up the contacts of the track relay TR, while it is also such thatthe contacts of the detector relay KR are shifted. to their lefthand ornormal position as shown.

On picking up of the track relay contacts contact l5 establishesconnection from terminal B of a local source of direct current, notshown, to one terminal of the primary winding of the decodingtransformer DT, while contact l6 establishes a circuit to supply energyfrom the transformer secondary winding to relay H. The center terminalof this winding is connected to terminal C of the source so thatone-half of the transformer primary winding is energized and an impulseof energy is induced in each of the transformer secondary windings.

The impulse of energy induced in secondary winding ll of the transformeris supplied to the impulse relay IR. However, the relay IR is of a typethe contacts of which become picked up only when energy of one polarityis supplied to the relay winding and the various parts of the equipmentare arranged so that the energy supplied to the relay IR on movement ofthe track relay contacts to their picked-up positions is of suchpolarity as to be ineffective to pick up the contacts of relay IR.

Similarly, on movement of contact E3 of relay KR to its left-handposition a circuit is estalb lished to energize one portion of theprimary winding of transformer KT from a local source of direct current,not shown, while contact 19 of the relay KR establishes a circuit tosupply energy from the secondary winding of transformer KT to theapproach relay AR.

After a brief time interval, the contact ll] of coding relay CR moves toits released position, thereby interrupting the supply of energy fromthe track battery TB over the circuit traced above, while contact lflconnects the winding of the relay KR across the track rails l and 2. Onthis interruption in the supply of energy from the battery TB thecontacts of track relay TR release and contact l5 establishes a circuitto energize the other portion of the primary winding of transformer DT,As a. result, an impulse of energy is induced in each of the transformersecondary windings. These impulses are of the polarity opposite to thatof the impulses present on movement of the track relay contacts to theirpickedup positions, and accordingly the energy supplied to the relay IRis effective to pick up the contacts of this relay.

.On picking up of the contacts of relay IR contact l2 interrupts thecircuit traced above for connecting the Winding of the track relay TRacross the track rails and establishes a circuit to supply energy fromthe battery IE to the relay KR over the rails l and 2. This circuit istraced from the positive terminal of the battery IB through frontcontact E2 of relay IR, winding of relay TR, track rail I, winding ofrelay KR, back contact if) of KR to their reverse or right-handpositions.

relay CR, track rail 2 and resistance 21 to the other terminal of thebattery IB. At this time, therefore, the relay KR is energized bycurrent supplied fromjthe battery IB. The direction of flow of thisenergy through the winding of the relay KR is opposite to that of theenergy supplied to the relay KR from the track battery TB andaccordingly the contacts of the relay KR are shifted to their right-handor reverse positions so that contact 58 establishes a circuit toenergize the other portion of the primary winding of transformer KT.while contact is establishes a circuit to supply energy from thetransformer secondary winding to the approach relay AR.

In addition, at this time the track relay TR is energized by currentsupplied from the impulse battery IR. However, the direction of flow ofenergy through the relay winding is such that the energy is ineffectiveto pick up the relay contacts, but on the contrary serves to hold thesecontacts more firmly in their released positions.

After a brief time interval, the contacts of relay IR release andinterrupt the supply of energy from the battery IE to the section rails,while contact 52 reconnects the track relay TR across the section rails.On this interruption of the supply of energy from the battery 13 energyceases to be supplied to the relay KR, but because of thecharacteristics of the relay the contacts of this relay remain in theposition to which they have just been moved.

Subsequently, the contact Ill of relay CR picks up and interrupts thecircuit connecting the relay KR across the section rails and againestablishes the circuit for supplying energy from the battery TB to therelays KR and TR in series.

As long as the track section is vacant, the equipment continues tooperate in this manner. The track relay contacts pick up on the supplyof impulses of master code energy, While these energy impulses effectmovement of the contacts of the detector relay KR to their left-hand ornormal positions. During the off intervals between the impulses ofmaster code the track relay contacts release, while the impulse relaycontacts pick up and disconnect the track relay from the track rails andestablish the circuit to supply an impulse of feed-back energy from thebattery IE to the relay KR. These impulses of feed-back energy effectmovement of the contacts of relay As a result of picking up andreleasing of the track relay contacts, energy is supplied through thetransformer DT to the relay I-I, while as a result of movement of thecontacts of the detector relay KR between their normal and reversepositions, energy is supplied through the transformer KT to the relayAR. The relays AR and H are of a type a which are somewhat slow inreleasing so that their contacts remain picked up during the intervalsbetween the supply of impulses of energy thereto. As long as the tracksection is vacant, therefore, the relays H and AR are picked up.

When a train moving in the normal direction of trafhc, that is from leftto right, enters the section, the wheels and axles of the vehicles ofthe train shunt the track relay TR so that its Eontacts thereafterremain released, Accordingly, impulses of energy are not suppliedthrough the transformer DT to the'impulses relay IR and the contacts ofrelay IR remain released and do not supply impulses of feedback energyto the section rails and to the relay KR. In addition, energy is notsupplied through the transformer DT to the relay H and the contacts ofrelay H release.

At this time the coding relay CR continues to operate and to supplyimpulses of master code energy to the sectionrails. These impulses ofenergy cause the contacts of relay KT to move to their left-hand ornormal positions. However, at this time, as impulses of feed-back energyare not supplied to the relay KR, the contacts of this relay remain intheir left-hand or normal positions and no energy is supplied from thetransformer KT to the approach relay AR. Accordingly, the contacts ofthe relay AR release and interrupt or establish the approach controlcircuits.

When the train advances far enough to vacate the section, the impulsesof master code energy feed to the track relay TR and produce codefollowing operation of this relay so that energy is supplied through thetransformer DT to the relays H and IR, while the relay IR operates tosupply impulses of feed-back energy to the relay KR over the sectionrails so that energy is again supplied through the transformer KT to therelay AR. Accordingly, the relays H and AR are picked up when the tracksection is vacated.

In this system the polarity of the master code and feed-back energy issuch that there is no possibility of improper operation of the detectorreiay by energy stored in the track circuit when the track section isoccupied.

When contact it of coding relay CR is picked up, energy flows from thepositive terminal of the battery TB through the contact i9 and thewinding of detector relay KR to track rail l, thence through the wheelsand axles of a train present in the track section to track rail 2 and tothe negative terminal of the battery,

When contact iii of the coding relay CR moves out of engagement with itsfront contact, this circuit is interrupted, but because of theinductance of the track circuit and the conductance of the ballasttoward the exit end of the track circuit, current continues to flow inthis circuit for a period of time so that under most ballast conditions,when the contact Ill reengages its back contact, energy stored in thetrack circuit will flow for a short period of time through the windingof the detector relay KR. The direction of flow of this energy is thesame as that supplied from the track battery so that the only effect ofthe energy is to maintain the detector relay contacts in the position towhich they have already been moved. Accordingly, no change inenergization of the primary winding of transformer KT occurs and energywill not be supplied to the relay AR.

This circuit is also arranged so that, if the contacts of the relay CRare incorrectly adjusted or build up and the movable contact it! engagesits front and back contacts at the same time, improper operation of therelay KR cannot occur.

Referring to the drawings, it will be seen that, if the front and backcontacts of relay CR overlap, the track battery TB will be shortcircuited through the resistance l4, while no circuit will beestablished to improperly energize the relay KR.

Similarly, the circuit provided by my invention is arranged so that, ifcontact l2 of relay IR is incorrectly adjusted or builds up so that itengages its front and back contacts at the same time, the track relay TRcannot be energized from the battery IR. The only result of thisconditions is to short circuit the battery 13 through the resistance 2!.

The entrance end equipment provided by this invention isarranged so thatenergy stored in the track circuit cannot cause undesired operation ofthe track relay. This problem is not present when a train enters theentrance end of the track section in the usual manner since the trackrelay is shunted and the impulse of feed-back energy supplied to thetrack rails does not flow far enough in the track rails to cause anappreciable amount of energy to be stored in the track circuit, As thetrack relay is shunted it remains released and no further impulses ofenergy are supplied to the impulse relay so the impulse relaycontactsremain released and do not supply additional impulses offeed-back energy to the section.

However, if a train backs into a section, or if a section includes aswitch at an intermediate point and a train enters the section throughthe switch, the track relay contacts will release and energy will besupplied to the impulse relay so that its contacts pick up and cause animpulse of feed-back energy to be supplied to the section rails. Thiimpulse of feed-back energy will be prevented from reaching the detectorrelay due to the presence of the train in the track section. However, asthe train is some distance removed from the entrance end of the sectionthe feedback energy flows through a substantial part of the trackcircuit and considerable energy may be stored in the track circuit.

On sub-sequent release of the impulse relay contacts the supply ofenergy from the impulse battery to the track rails is cut off while thetrack relay winding is connected across the section rails. As explainedin connection with the equipment at the exit end of the section, theenergy stored in the track circuit flows in the same direction as theenergy supplied from the battery to the section rails. Accordingly, theenergy in the track circuit will flow through the track relay winding inthe wrong direction to pick up the relay contacts. The track relaycontacts, therefore, remain released and no energy is supplied to theimpulse relay so the contacts of the impulse relay remain released andno more impulses of feed-back energy are supplied to the section rails.

In Fig. 2 of the drawings there is shown a modified form of apparatuswhich I may employ at the entrance end of the track section. Thisapparatus is substantially the same as that shown in Fig. 1, but difierstherefrom in that the impulse relay IR has a contact [3, which whenpicked up short circuits the winding of the track relay TR. Accordingly,the impulses of feedback energy need not flow through the track relaywinding, but may flow through the circuit established by contact I3. Thecircuit established by contact I3 is of much lower resistance than thecircuit of the track relay winding so that the impulses of energysupplied from the battery IE to the track rails are stronger when thecircuit shunting the track relay Winding is employed than when thiscircuit is not provided. Accordingly, the circuit provided by contact i3makes it possible to employ the equipment on longer track circuits thanwould be possible without this circuit.

In Fig. 3 of the drawings there is shown a modified form of equipmentwhich may be employed at the exit end of the track section. Thisequipment is similar to that shown in Fig. 1, but differs therefrom inthat the contact l8 of detector relay KR'directly'controls the supply ofenergy to the approach relay instead of controlling the supply of energythereto through a transformer.

In this modification the circuit of the relay AR is arranged so that itis complete when contact I8 of detector relay KR is in the position towhich it is moved by the impulses of feed-back energy. Accordingly, aslong as the track section is vacant and impulses of feed-back energyreach the detector relay KR, impulses of energy will be supplied to theapproach relay AR and the contacts of this relay will be maintainedpicked up. During the periods in which the detector relay contact i8 isin its left-hand or normal position as a result of the supply ofimpulses of master code energy to the relay winding, en-

ergy is not supplied to the relay AB. The relay AB is of a type thecontacts of which are slow in releasing, however, and remain picked upduring these periods.

When a train enters the section the supply of impulses of feed-backenergy to the detector relay is out off, and the relay contact is movedto its left-hand or normal position by the impulses of master codeenergy to thereby cut off" the supply of energy to the approach relay.As the detector relay contact remains in its normal position theapproach relay is deenergized and its contacts release.

In Fig. 4 of the drawings there is shown a different form of apparatuswhich may be employed at the exit end of the section. This equipmentdiffers from that shown in Figs. 1 and 3 in that a different type ofdetector relay is employed. In the system shown in Fig. 4 the detectorrelay KRA is similar to the track relay and is of a type the contacts ofwhich when released become picked up only when energy flows in onedirection through the relay winding, and which when picked up becomereleased on interruption of the supply of energy to the relay winding oron the supply of energy of the opposite polarity to the relay Winding.

The exit end equipment shown in Figs. l, 5 and 6 is intended to be usedwith entrance end equipment of the type shown in Figs. 1 and 2, while itis contemplated that the positive terminal of the impulse batteryassociated with the entrance end equipment will be connected to the sametrack rail as the positive terminal of the track battery associated withthe exit end facilities.

In operation when the coding relay contacts are picked up contact illestablishes a circuit to supply an impulse of master code energy fromthe battery TB to the section rails through the winding of the detectorrelay KRA. The direction of flow of energy in this circuit is such thatthe energy is ineffective to pick up the contacts of the detector relay,but instead tends to maintain them more firmly in their releasedposition.

On movement of the coding relay contact ii] to its released position thesupply of master code energy is interrupted, while the coding relaycontact iii connects the detector relay winding across the section railsso that on the supply of an impulse of feed-back energy by the equipmentat the entrance end of the section this energy may feed to the detectorrelay winding and pick up the contacts of this relay. On picking up ofthe contacts of relay KRA contact 25 establishes the circuit of theapproach relay AR.

On subsequent picking up of the contacts of the coding relay CR contacttil interrupts the circuit connecting the detector relay KRA across thesection rails and establishes the circuit connecting the track batteryacross the section rails in series with the detector relay winding sothat another impulse of master code energy is supplied to the sectionrails, while the contacts of the detector relay KRA release.

As long as the track section is vacant the equipment continues tooperate in this manner, that is, during the picked-up periods of thecoding relay contacts impulses of master code energy are supplied to thesection rails while the detector relay contacts release, and when thecoding relay contacts are released the detector relay winding isconnected across the section rails so that the relay contacts are pickedup by impulses of feed-back energy.

If desired, the modification shown in Fig. 4 may include a contact I Ion the coding relay CR and. effective when picked up to short circuitthe winding of the detector relay KRA so that the impulses of mastercode energy need not be supplied through the detector relay winding. Asexplained in connection with the entrance end equipment of Fig. 2, thiscircuit increases the value of the master code impulses so that thelength of the track circuit may be increased.

The modification shown in Fig. 4, like those shown in Figs. 1 and 3,operates so that energy stored in the track circuit cannot improperlyenergize the detector relay when the section is occupied, and so thatoverlapping contacts on the coding relay cannot produce false operationof the detector relay.

As explained in connection with the apparatus shown in Fig. 1, theenergy stored in the track circuit when the section is occupiedcontinues to flow in the same direction as the master code energy sothat when coding relay contact H] is moved to its released position anyflow of energy in the detector relay winding as a result of storedenergy in the track circuit will flow in the wrong direction to pick upthe contacts of this relay. In addition, it will be seen from thedrawings that if the front and back contacts of the coding relay contactlt overlap a circuit will be established to short circuit the trackbattery, while no circuit will be established to supply energy to thedetector relay which will result in picking up of the contacts of thisrelay.

The detector relay shown in Fig. 4 is provided only with a pick-upwinding, and the contacts of this relay remain picked up only as long asthe impulse of feed-back energy is maintained. These impulses may be ofvery brief duration with the result that the relay contacts will bepicked up for only short periods. It may be desired to prolong thepicked-up periods of the detector relay contacts as much as possible,and the modification shown in Fig. 5 provides means to do so.

Referring to Fig. 5, the detector relay KRA employed therein is providedwith a pick-up winding which is connected with the track rails in thesame manner as the relay shown in Fig. 4. This relay has, in addition, aholding winding, while a circuit controlled by contact 25 of thedetector relay and by contact 26 of the coding relay is provided forenergizing the detector relay holding winding and the winding of theapproach relay AR.

In operation, on release of the coding relay contacts and the supply ofan impulse of feedback energy to the pick-up winding of the detectorrelay KRA contact 25 of this relay picks up and establishes the circuitof the holding Winding of the detector relay and of the approach relaywinding. This circuit is traced from terminal B of a local source ofdirect current, which may be the track battery, through the holdingWinding of the detector relay KRA, back contact 26 of coding relay CR,winding of approach relay AR, and front contact 25 of the detector relayKRA to terminal C of the source. Accordingly, the holding winding of thedetector relay and the winding of the approach relay are energized inseries. The holding winding of the detector relay when energized assistsin maintaining the relay contact picked up so that if the impulse offeed-back energy terminates before the coding relay contacts pick up thedetector relay contact will be maintained picked up by the relay holdingwinding and energy will continue to be supplied to the approach relaywinding.

On picking up of the coding relay contacts contact 26 interrupts thecircuit of the detector relay holding winding and of the approach relaywinding, while contact it interrupts the circuit of the detector relaypick-up winding so that the contact 25 releases and additionallyinterrupts the circuit of the holding winding and of the approach relay.

It will be seen that the provision of the holding winding on thedetector relay insures that the detector relay contact will remainpicked up as long as the coding relay contacts remain released. Thisprolongs the time of energization of the approach relay andcorrespondingly reduces the period during which the approach relaycontacts must remain picked up in order to bridge the intervals betweenthe impulses of energy supplied thereto.

The modification shown in Fig. employs a detector relay having a singlecontact to control the circuit of both the detector-relay holdingwinding and the approach relay winding. It may be preferred to employseparate contacts to control the circuits of these windings and Fig. 6shows means to control these circuits in this manner.

This modification is substantially the same as that shown in Fig. 5 andemploys a detector relay having a pick-up and a holding winding. Thecircuit of the holding winding is controlled by contact 26 of the codingrelay CR and by contact 21 of the detector relay so that on picking upof the detector relay contacts the holding winding of the relay isenergized and maintains the relay contacts picked up as long as thecoding relay contacts are released. In addition, on picking up of thedetector relay contacts contact 25 establishes the circuit of theapproach relay AR so that this relay is energized as long as thedetector relay contacts are picked up.

On picking up of the coding relay contacts the circuit of the detectorrelay holding winding is interrupted and contacts 25 and 2! release andinterrupt the circuit of the approach relay and additionally interruptthe circuit of the detector relay holding winding.

The modifications shown in Figs. 4, 5 and 6 make it possible to supplyalternating current energy to the track circuit for cab signal purposes,and the manner in which this is done is shown in Fig. 6 of the drawings.It should be understood. however, that this means is equally applicableto the modifications shown in Figs. 4 and 5;

Referring to Fig. 6, it will be seen that a track transformer TT isprovided and that the secondary winding of this transformer is includedin series with the track battery. The primary winding. of thistransformer is connected to a source of alternating current of suitablefrequency, the terminals of which are designated BX and CK.

In operation when the coding relay contacts are picked up the trackbattery TB and the track transformer TT are connected cross the sectionrails by contact 10 of the coding relay, while contact ll of the codingrelay short circuits the detector relay winding to provide a lowresistance.

circuit for the supply of energy to the track circuit and to prevent theimpulses of alternating current from effecting picking up of thedetector relay contacts.

When the coding relay contacts are released the supply of direct andalternating current energy to the track rails is cut off, while contactl0 connects the pickup winding of the detector relay across the sectionrails.

In the drawings of this application there are shown in Figs. 1 and 2 twoforms of equipment which may be employed at the entrance end of a tracksection, while Figs. 1, 3, 4, 5 and 6: show various forms of equipmentwhich. may be employed at the exit end of a section. It should beunderstood that either form of exit end equipment may be employed witheither form of entrance and equipment.

The exit end equipment shown in Figs. 1 and 3 employs a detector relayof the polarized type the contacts of which are moved to one position.

on flow of energy in the direction through the relay winding and aremoved to a second position on flow of energy in the other directionthrough the relay winding, while on deenergization of the relay windingthese contacts remain in the position to which they have last beenmoved.

The modifications shown in Figs. 4, 5 and 6 employ a biased polar relaythe contacts of which are normally released and become picked up only onhow of energy in one direction through the relay winding, while therelay contacts when picked up become released on deenergization of therelay or on flow of energy in the relay winding in the directionopposite to that effective to pick up the relay contacts.

It will be seen that the two types of detector relays are diiferent insome respects, but that they have one characteristic in common, that isthat each is uniquely responsive to flow of energy in one directionthrough the winding thereof, The contacts of the polar type detectorrelay KR when in their normal position are shifted to their reverseposition on the supply of an impulse of feed-back energy to the relaywinding. Similarly, the contacts of the biased polar type detector relayKRA when released become picked up on the supply of an impulse offeed-back energy to the relay winding.

Although I have herein shown and described several forms of railwaysignaling system embodying my invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

1. In a coded railway signaling system, in combination, a section ofrailroad track having a first and a second track rail over which trafiicnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the section, a codefollowing detector relay and a track battery located at the exit end ofthe section, continuously operating coding means having a contacteffective in one position to connect the detector relay winding acrossthe section rails and effective in another position to connect the trackbattery across the section rails in series with the detector relaywinding, an impulse relay associated with the track relay, meanseffective on release of the track relay contacts to supply energy to theimpulse relay, said impulse relay having a contact effective whenreleased to connect the track relay winding across the section rails andeffective when picked up to connect the impulse battery across thesection rails in series with the track relay winding, the track relayand detector relay each being of a type which is uniquely responsive toflow of energy in one direction through the winding thereof and eachbeing connected with the track rails in such manner that when energyflows from the first to the second track rail through the winding energyflows through the winding in said one direction, the track battery andimpulse battery each being arranged so that when the battery isconnected across the track rails the positive terminal thereof isconnected to said first track rail, an approach relay, and meansgoverned by a contact of said detector relay for supplying energy tosaid approach relay.

2. In a coded railway signaling system, in combination, a section ofrailroad track having a first and a second track rail over which trafiicnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the section, a codefollowing detector relay and a track battery located at the exit end ofthe section, continuously operating coding means having contacts movablebetween a first and a second position, said means having a contacteffective in its first position to connect the detector relay windingacross the section rails and being effective in its second position toconnect the track battery across the section rails in series with thedetector relay winding, said coding means having another contacteffective in said second position to short circuit the detector relaywinding, an mpulse relay associated with the track relay, meanseffective on release of the track relay contacts to supply energy to theimpulse relay, said impulse relay having a contact effective whenreleased to connect the track relay winding across the section rails andeffective when picked up to connect the impulse battery across thesection rails in series with the track relay winding, the track relayand-detector relay each being of a type the contacts of which becomepicked up only on flow of energy in one direction through the relaywinding and each being connected with the track rails in such mannerthat when energy flows from the first to the second track rail throughthe relay winding energy fiows through the winding in said onedirection, the track battery and impulse battery each being arranged sothat when the battery is connected across the track rails the positiveterminal thereof is connected to said first track rail, an approachrelay, and means governed by a contact of said detector relay forenergizing said approach relay.

3. In a coded railway signaling system, in combination, a section ofrailroad track having a first and a second track rail over which trafficnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the section, a codefollowing detector relay and a track battery located at the exit end ofthe section, continuously operating coding means having a contacteffective in one position to connect the detector relay winding acrossthe section rails and effective in another position to connect the trackbattery across the section rails in series with the detector relaywinding, an impulse relay having normally released contacts, meanseffective on release of the track relay contacts to supply energy to theimpulse relay, a contact of said impulse relay being effective whenreleased to connect the track relay winding across the section rails andbeing effective when picked up to connect the impulse battery across thesection rails in series with the track relay winding, said impulse relayhaving another contact effective when picked up to short circuit thetrack relay winding, the track relay and the detector relay each beingof a type which is uniquely responsive to flow of energy in onedirection through the winding thereof and each being connected with thetrack rails in such manner that when energy flows from the first to thesecond track rail through the relay winding energy flows through thewinding in said one direction, the track battery and impulse batteryeach being arranged so that when it is connected across the sectionrails the positive terminal thereof is connected to said first trackrail, an approach relay, and means governed by a contact of saiddetector relay for energizing said approach relay.

4. In a coded railway signaling system, in combination, a section ofrailroad track having a first and a second track rail over which trafiicnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the section, a codefollowing detector relay and a track battery located at the exit end ofthe section, continuously operating coding means having contacts movablebetween a first and a second position, said means having a contacteffective in its first position to connect the detector relay windingacross the section rails and effective in its second position to connectthe track battery across the section rails in series with the detectorrelay winding, said means having another contact eifective in saidsecond position to short circuit the detector relay winding, an impulserelay having normally released contacts, means effective on release ofthe track relay contacts to supply energy to said impulse relay, acontact of said impulse relay being effective when released to connectthe track relay winding across the section rails and being eifectivewhen picked up to connect the impulse battery across the section railsin series with the track relay winding, said impulse relay havinganother contact effective when picked up to short circuit the trackrelay winding, the track relay and detector relay each being of a typethe contacts of which become picked up only on flow of energy in onedirection through the relay winding and each being connected with thetrack rails in such manner that when energy flows from the first to thesecond, track rail through the relay winding energy flows through thewinding in said one direction, the track battery and impulse batteryeach being arranged so that when it is connected across the sectionrails the positive terminal thereof is connected to said first trackrail, an approach relay, and means governed by a contact of saiddetector relay for supplying energy to said approach relay.

5. In a' coded railway signaling system, in combination, a section ofrailway track over which traflic normally moves in one direction, a codefollowing track relay and an impulse battery located at the entrance endof the section, a polarized code following detector relay and a trackbattery located at the exit end of the section, said detector relayhaving a contact movable to one position on flow of energy in onedirection through the relay winding and movable to its other position onflow of energy in the other direction through the relay winding,continuously operating coding means operative at one time to connect thetrack battery across the section rails in series with the detector relaywinding to thereby energize the detector relay and to supply energy overthe track rails to the track relay, said coding means being operative atother times to connect the detector relay winding across the trackrails, means operative on release of the track relay contacts toestablish a circuit to supply energy from the impulse battery over thetrack rails to the detector relay winding, the equipment being arrangedso that the energy supplied to the detector relay from the impulsebattery is of the polarity effective to move the detector relay contactto its one position and so that the energy supplied to the detectorrelay from the track battery is of the polarity effective to move thedetector relay contact to its other position, an approach relay,

and means governed by a contact of said detector relay for supplyingenergy to said approach relay.

6. In a coded railway signaling system, in combination, a section ofrailway track over which traffic normally moves in one direction, a codefollowing track relay and an impulse battery located at the entrance endof the section, a polarized code following relay and a track batterylocated at the exit end of the section,

said detector relay having a contact movable to one position on flow ofenergy in one direction through the relay Winding and movable to itsother position on flow of energy in the other direction through therelay winding, continuously operating coding means operative at one timeto supply energy from the track battery to the detector relay and toalso establish a circuit to supply energy from the track battery overthe track rails to the track relay, said coding means being operative atother times to connect the detector relay winding across the trackrails, means operative on release of the track relay contacts toestablish a circuit to supply energy from the impulse battery over thetrack rails to the detector relay winding, the equipment being arrangedso that the energy supplied to the detector relay from the impulsebattery is of the polarity effective to move the detector relay contactto its one position and so that the energy supplied to the detectorrelay from the track battery is of the polarity effective to move thedetector relay contact to its other position, an approach relay, andmeans governed by a contact of said detector relay for supplying energyto said approach relay.

'7. In a coded railway signaling system, in combination, a section ofrailway track having a first and a second track rail over which traiiicnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the track section, apolar ized code following detector relay and a track battery located atthe exit end of the section, said detector relay having a contact whichis moved to one position when energy flows through the relay winding inone direction and which is moved to its other position when energy flowsthrough the relay winding in the other direction, continuously operatingcoding means effective at one time to connect the track battery acrossthe section rails with the detector relay winding in series with theconnection from one terminal of the battery to one track rail and withthe positive terminal of the battery connected to said first rail, saidcoding means being operative at other times to connect the detectorrelay winding across the section rails, means effective on release ofthe track'relay contacts to connect the impulse battery across thesection rails with the track relay winding in series with the connectionfrom one terminal of the battery to one track rail and with the positiveterminal of said track battery connected to said first rail, said meansbeing effective at other times to connect the track relay winding acrossthe section rails, an approach relay, and means governed by a contact ofsaid detector relay for supplying energy to said approach relay.

8. In a coded railway signaling system, in combination, a section ofrailway track having a first and a second track rail over which trafiicnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the section, a polarizedcode following detector relay and a track battery located at the exitend of the section, said detector relay having a contact which is movedto one position when energy flows through the relay winding in onedirection and which is moved to its other position when energy flowsthrough the relay winding in the other direction, the track relay havingone terminal of its winding connected to one track rail of said sectionand the detector relay having one terminal of its winding connected toone track rail of said section, continuously operating coding meanseffective at one time to connect the other terminal of the detectorrelay winding to the other track rail in series with the track batteryso that the positive terminal of the track battery is connected to saidfirst track rail to thereby energize the detector relay with current ofone polarity and to supply energy over the track rails to the trackrelay, said coding means being effective at other times to connect saidother terminal of said detector relay winding directly to said othertrack rail, means effective on release of the track relay contacts toconnect the other terminal of the track relay winding to the other trackrail in series with said impulse battery so that the positive terminalof said battery is connected to said first track rail to thereby supplyenergy of the other polarity from said impulse battery over the trackrails to the detector relay winding, said means being effective at othertimes to connect said other terminal of the track relay winding directlyto said other track rail, an approach relay, and means governed by acontact of said detector relay for energizing said approach relay.

9. In a coded railway signaling system, in combination, a section ofrailway track over which traffic normally moves in one direction, a codefollowing track rela and an impulse battery located at the entrance endof the section, a polarized code following detector relay and a trackbattery located at the exit end of the section, said detector relayhaving a contact movable to one position when the relay winding isenergized with current of one polarity and movable to its other positionwhen the relay'winding is energized with current of the other polarity,means for connecting the track relay winding across the section rails,means for connecting the detector relay winding across the sectionrails, continuously operating coding means effective at times to connectthe track battery across the section rails and to supply to the detectorrelay winding energy of one relative polarity, means effective onrelease of the track relay contacts to supply from the impulse batteryover the track rails to the winding of the detector relay energy of theother polarity, an approach relay, and means governed by a contact ofsaid detector relay for supplying energy to said approach relay.

10. In a coded. railway signaling system, in combination, a section ofrailway track over which traffic normally moves in one direction, a codefollowing track relay and an impulse battery located at the entrance endof the section, a polarized code following detector relay and a trackbattery located at the exit end of the. section, said detector relayhaving a contact movable to one position when the relay winding isenergized with current of one polarity and movable to its other positionwhen the relay winding is energized with current of the other polarity,means for connecting the track relay winding across the section rails,means for connecting the detector relay winding across the sectionrails, continuously operating coding means effective at times to connectthe track battery across the section rails and to supply to the detectorrelay winding energy of one relative polarity, means effective onrelease of the track relay contacts to supply from the impulse batteryover the track rails to the winding of the detector relay energy of theother polarity, an approach relay, a transformer, a'circuit complete inone position of said detector relay contact for supplying energy from asource of direct current to the primary winding of said transformer, andmeans for supplying energy from the secondary winding of saidtransformer to said approach relay.

11. In a coded railway signaling system, in combination, a section ofrailroad track having a first and a second track rail over which trafficnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of said section, a codefollowing detector relay and a track, battery at the exit end of thesection, said track relay and said detector relay each being of a typewhich is uniquely responsive to flow of energy in one direction throughthe winding thereof, means forv connecting the winding of each of saidrelays across the section rails in such manner that when energy flowsfrom said first track .rail through the relay winding to said secondtrack rail energy fiows through the relay winding in said one direction,continuously operating coding means effective at times to interrupt theconnection from one terminal of the detector relay winding to one of thetrack rails and to establish connection from said terminal to said trackrail including in series therewith the track battery, said connectionbeing arranged so that the positive terminal of said battery isconnected to said first track rail, means effective on release of thetrack relay contacts to interrupt the connection from one terminal ofthe track relay winding to one of the track rails and to establishconnection from said terminal to said track rail including in seriestherewith the impulse battery, said connection being arranged so thatthe positive terminal of said battery is connected to said first trackrail, an approach relay, and means governed by a contact of saiddetector relay for supplying energy to the approach relay.

12. In a coded railway signaling system, in combination, a section ofrailroad track over which trafiic normally moves in one direction, acode following track relay and an impulse battery located at theentrance end of the section, means for connecting the track relaywinding across the section rails, means effective on release of thetrack relay contacts to connect the impulse battery across the sectionrails with the positive terminal of the battery connected to said firsttrack rail, a code following detector relay, a track battery and acontinuously operating coding device located at the exit end of thesection, said detector relay being of a type which is uniquelyresponsive to fiow of energy in one direction through the windingthereof, said detector relay having one terminal of its windingconnected to one of said track rails, said coding device having contactswhich are moved between a first and a second position, a contact of saidcoding. device being effective when in its first position to connect theother terminal of said relay winding directly to the other track rail tothereby connect said detector relay winding across the track rails sothat when energy flows from the first rail through the relay winding tothe second rail energy flows through the relay winding in said onedirection, said coding device contact being effective when in its secondposition to connect said other terminal of said relay winding to saidother track rail in series with said track battery, said track batterybeing included in said circuit in such manner that the positive terminalthereof is connected to said first track rail, an approach relay, andmeans governed by a contact of said detector relay for energizing saidapproach relay.

13. In a coded railway signaling system, in combination, a section ofrailroad track having a first and a second track rail over which trafficnormally moves in one direction, a code following track relay and animpulse battery located at the entrance end of the section, a codefollowing detector relay and a track battery located at the exit end ofthe track section, one terminal of the detector relay winding beingconnected to one track rail, one terminal of the track battery beingconnected to the other track rail, a continuously operating codingdevice having a contact movable between a first and a second position,said coding device contact being effective when in its first position toconnect the other terminal of said detector relay to said other trackrail and being effective when in its second position to connect theother terminal of said relay winding to the other terminal of the trackbattery to thereby connect the battery across the section rails inseries with said detector relay winding, the track battery beingconnected across the section rails in such manner that the positiveterminal thereof is connected to said first track rail, one terminal ofthe track relay winding being connected to one track rail, one terminalof the impulse battery being connected to the other track rail, animpulse relay having a contact normally occupying a first position,

means efiective on release of the track'relay for moving the impulserelay contact to asecond position, said impulse relay contactbeing-effective when in said first position to connect the otherterminal of the track relay winding to the other track rail and beingeffective when in said second position to connect said other terminal ofthe track relay winding to the other terminal of said impulse battery tothereby connect the impulse battery across the section rails in serieswith the track relay winding, the track battery being connected acrossthe section rails in such manner that the positive terminal of thebattery is connected to said first track-rail, the track and detectorrelays each being of a type uniquely responsive to flow of energy in onedirection through the winding thereof and each being connected to thetrack rails in such manner that when energy flows from said first railthrough the relay winding to the second rail energy flows through thewinding in said one direction, an approach relay, and means governed bya con tact of said detector relay for supplying energy to said approachrelay.

14. In a coded railway signaling system, in combination, a section ofrailway track over which traffic normally moves in one direction, a codefollowing track relay and an impulse battery located at the entrance endof the section, means for connecting the track relay winding across thesection rails, means efiective on release of the track relay contacts toconnect the impulse battery across the section rails with the positiveterminal of the battery connected to said first track rail, a codefollowing detector relay, a track battery and a continuously operatingcoding device located at the exit end of the section, said detectorrelay having a contact movable between a first and a second position,said detector relay being of a type the contact of which when in itsfirst position is moved to its second position when and only when energyflows through the relay winding from its first to its second terminal,the first terminal of said detector relay winding being connected tosaid first track rail, the negative terminal of said track battery beingconnected to said second track rail, said coding device having a contactwhich is moved between two positions, said coding device contact beingeffective when in one of its positions to connect the second terminal ofsaid detector relay winding to the positive terminal of said trackbattery and being efiective when in its other position to connect thesecond terminal of said detector relay winding to said second trackrail, an approach relay, and means governed by said detector relaycontact for energizing said approach relay.

15. In a coded railway signaling system, in combination, a section ofrailway track over which traffic normally moves in one direction, a codefollowing track relay, an impulse relay and an impulse battery locatedat the entrance end of said track section, said track relay being of atype the contacts of which pick up when and only when energy flowsthrough the relay winding from its first to its second terminal, thefirst terminal of said track relay winding being connected to the firsttrack rail, the negative terminal of said impulse battery beingconnected to the second track rail, a contact of said impulse relay be"ing effective when released to connect the second terminal of the trackrelay winding to the second track rail and being effective when pickedup to connect the second terminal of said track relay winding to thepositive terminal of said impulse battery, means effective on release ofthe track relay contacts to supply an impulse of en ergy to said impulserelay, a code following detector relay, a track battery and acontinuously op erating coding device located at the exit end of saidtrack section, said detector relay having a contact movable between afirst and a second position, said detector relay being of a type thecontact of which when in its first position is moved to its secondposition when and only when energy flows through the relay winding fromits first to its second terminal, the first terminal of said detectorrelay winding being connected to the first track rail, the negativeterminal of said track battery being connected to said second trackrail, said coding device having a contact which is moved between twopositions, said coding device contact being efiective when in one of itspositions to connect the second terminal of said detector relay windingto the positive terminal of said track battery and being effective whenin its other position to connect the second terminal of said detectorrelay winding to said second track rail, an approach relay, and meansgoverned by said detector relay contact for energizing said approachrelay.

FRANK H. NICHOLSON.

